1. Field of the Invention
The present invention is directed to a method for producing a print image on a carrier material, whereby ink-attracting and ink-repelling areas are produced on a surface of a print medium according to the structure of the print image to be printed, whereby the ink-repellant areas are provided with a layer of an ink-repellant medium, ink is applied onto the surface, this adhering to the ink-attracting areas and not being picked up by the ink-repellant areas, and whereby the ink distributed on the surface is printed onto the carrier material.
The invention is also directed to an apparatus for producing a print image on a carrier material.
2. Description of the Related Art
Given a known offset printing process which works without water, the areas not to be printed are fat-repellant, they do not accept any ink. The areas to be printed, by contrast, are fat-attracting and can accept fat-containing ink. The ink-attracting and ink-repellant areas are distributed on a printing plate such that they reproduce the print image to be printed. The printing plate can be employed for a plurality of transfer printing events. A new printing plate with ink-attracting and ink-repellant areas must be produced for each print image.
Given the known direct imaging method of Heidelberger Druckmaschinen, a print master is produced in the printing system on a silicone-coated film by partially burning the silicone layer off. The silicone-free locations form the color-attracting areas and can pick color up during the printing process.
In another offset process working with water, hydrophobic and hydrophilic areas corresponding to the structure of the print image to be printed are produced on the print medium. Before applying ink to the print carrier, a thin moisture film is first applied onto the print carrier by employing application rollers or, respectively, sprayer devices, this wetting the hydrophilic area of the print carrier. With the assistance of an inking roller, ink is subsequently applied onto the surface of the print carrier; this, however, moistens only the areas not covered with the moisture film. After the inking of the print carrier, the ink print image is finally transferred onto the carrier material.
A method developed by Oce Printing Systems GmbH is also known wherein hydrophobic and hydrophilic areas are formed on the surface of the print carrier. The hydrophilic areas are moistened, so that no ink adheres to them. The surface of the print carrier is charged with water steam for moistening. The charging with water steam can also ensue such that hydrophilic areas arise corresponding to the structures of the print image to be printed. The ink is only picked up by areas that have not been provided with a moisture film. The aforementioned methods have the problem that the ink-water equilibrium must be very narrowly toleranced in order to achieve a high printing quality.
British patent document GB-A-1208731 discloses a method or, respectively, an apparatus for producing a print image on a carrier material. A substance in its solid phase is applied on a surface of a carrier material. This substance is heat sensitive and can be structured according to predetermined picture elements under the influence of heat, whereby this solid substance is removed. The uncovered surface of the print carrier can be brought into a hydrophilic condition. When inking with ink particles containing water, these adhere to the hydrophilic areas, whereas the hydrophobic areas of the substance in its solid phase repel these ink particles.
U.S. Pat. No. 3,741,118 discloses and method and an apparatus for printing an image, whereby a technique is utilized that approximately corresponds to a standard lithography technique. Upon application of electronic scanning technology, ink is selectively applied on a plate or an existing layer is selectively removed. The ink on the plate is then transferred onto paper. Subsequently, the plate is cleaned and can be prepared anew for the acceptance of ink.
An object of the present invention is to provide a method and an apparatus for producing a print image on a carrier material that produces print images with high resolution and is largely compatible with previous printing processes or, respectively, printing devices.
This object is achieved by a method for producing a print image on a carrier material, including the steps of: producing ink-attracting and ink-repellant areas on a surface of a print carrier in conformity with a structure of the print image to be printed, providing the ink-repellant areas with a layer of an ink-repellant medium, supplying ink onto the surface, the ink adhering to the ink-attracting areas and being not picked up by the ink-repellant areas, printing the ink distributed on the surface onto the carrier material, using a substance in its solid phase as an ink-repellant medium in the ink-repellant areas, cooling the surface of the print carrier to produce the solid phase of the substance on the surface of the print carrier.
The employment of a solid substance as an ink-repellant medium has the advantage that a sharp boundary arises between ink-attracting and ink-repellant areas, as a result whereof the resolution of the print image is enhanced. Given employment of a substance in its solid phase, further, this does not run dry and no water streaks arise as is possible given traditional printing processes. The procedure known from offset printing for inking the print carrier and for transfer printing onto a carrier material can be retained.
An ice layer is preferably employed as an ink-repellant medium, this being deposited by condensation of water vapor in the environment of the print medium by spraying a thin water film or by application of a water film with rollers and subsequent formation of ice on the surface thereof. This ice layer has a defined form and a defined volume and offers relatively great resistance to a shape or volume change under the influence of external forces since the water molecules in the solid aggregate state are firmly bonded to one another at specific locations by electromagnetic interactions. The ink-repellant areas can thus be produced with a fine structure that leads to a print image having a high resolution. The ice layer becomes extremely uniform and thin as a result of adding an agent for reducing the surface tension of the water, preferably tensides or alcohol. The additives are located directly in the water and/or are applied on the print carrier by spraying or, respectively, application with a roller. Solid parting agents such as waxes, fats, resins or fatty acid amides can be employed as a further ink-repellant medium, these being applied onto the print carrier in the liquid condition by spraying or application with one or more rollers. The medium will convert into its solid phase on the printing plate which is cooled to below the solidification temperature of the respective substance.
In a preferred exemplary embodiment of the invention, the print-active surface of the print carrier is initially completely provided with an ice layer or with a parting agent layer composed of wax, fat, resin or fatty acid amides. In a following structuring process, ink-attracting areas that are free of said solid layer, for example of the ice layer or of the parting agent layer, are produced. Ink-attracting areas corresponding to the structure of the print image to be printed can be produced in this way.
In this exemplary embodiment, the surface of the print carrier need not be pre-treated according to the structure of the print image to be printed, for example by etching. On the contrary, the print-active surface is uniform and smooth in the initial condition. The structuring process merely comprises the production of areas which are free of solid bodies or, respectively, free of ice in conformity with the structure of the print image to be printed. In accord therewith, a plurality of print images can be produced on the surface of the print carrier, whereby the initial condition of the surface of the print carrier is to be produced for each print image. In this way, different print images can be produced without replacing the print carrier and can be inked and transfer-printed once or repeatedly. When a new print image is to be applied on the print carrier, then the print carrier is to be cleaned of the areas provided with the solid state layer or, respectively, ice layer as well as of ink residues, the surface is to be provided again with a solid state layer or, respectively, ice layer, and a new structuring process ensues.
The gradient energy of a laser beam or of an LED can be employed for selectively producing areas which are free of solid bodies or, respectively, free of ice on the surface of the print carrier. Another possibility is comprised in selectively producing the areas free of solid bodies by employing heating elements.
According to a further aspect of the invention, a means for implementing the disclosed method is recited.